1. Field of the Invention
The present invention relates to spring drive, more particularly to a spring drive for use in a moving toy or the like.
2. Description of the Prior Art
A spring drives have been widely used as driving power sources, moving toys by the unwinding action of a spring which has been wound frictionally by rubbing the drive wheel against the floor.
There has been used a spring drive as shown in FIG. 6 comprising a pinion 2 provided around a wheel shaft 1, a spur gear 3 meshed with the pinion 2, a windup pinion 5a always meshed with the spur gear 3 and movably supported by a slit-shaped hole bearing 4a, a spring windup shaft 7a having a gear 6a meshed with the pinion 5a , a large 8a provided around the spring windup shaft 7a, a drive pinion 9a always meshed with the large gear 8a and movably supported by a slit-shaped hole bearing 22a, right and left side frames 11a and 12a supporting the gear trains, and a partition frame 13 interposed therebetween.
The conventional spring drive thus constructed has the partition frame 13 for supporting one end of the windup pinion 5a and one end of the drive pinion 9a. It is obviously desirable that this partition frame be eliminated in view of the easier assembly and lower production cost this would afford. In order to eliminate the partition frame, the windup pinion 5a and the drive pinion 9a must be supported by the right and left frames 11a and 12a. However, this inherently causes these two gears to collide with one another, and consequently the elimination of the partition frame has been impossible. For enabling emission of the partition frame, Japanese Utility Model Publication 1-28305 (corresponding to U.S. Pat. No. 4,623,039) provides a spring drive wherein, as shown in FIG. 7, a drive pinion 9b is supported by right and left frames 11b and 12b, a stepped portion 10b having a larger diameter than a gear 6 is formed between the gear 6b of a spring windup shaft and a large gear 8b, and one end of a windup pinion 5b is supported by the stepped portion 10b and a spur gear 20b, thereby eliminating the partition frame.
According to this conventional spring drive, the intermediate partition frame is effectively eliminated. However, as mentioned above, since the windup pinion 5b is supported by both the stepped portion 10b and the spur gear 20b, if the gears and other components are manufactured with very litter clearance, the friction will increase between the windup pinion, and the stepped portion and the spur gear and thus considerably decrease the rotation torque derived from the spring. Moreover, in this Japanese Utility Model Publication, although a projection or a recess is provided on each of the supporting surfaces for the windup pinion of the stepped portion 10b and the spur gear 20b and one end of the windup pinion 5b, there are nevertheless four contact points or surfaces so that little or no decrease in friction is realized.